CA2365119C - Dosing control for helical dosing equipment - Google Patents
Dosing control for helical dosing equipment Download PDFInfo
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- CA2365119C CA2365119C CA2365119A CA2365119A CA2365119C CA 2365119 C CA2365119 C CA 2365119C CA 2365119 A CA2365119 A CA 2365119A CA 2365119 A CA2365119 A CA 2365119A CA 2365119 C CA2365119 C CA 2365119C
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- mass flow
- rotational speed
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- helix
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F13/00—Apparatus for measuring by volume and delivering fluids or fluent solid materials, not provided for in the preceding groups
- G01F13/001—Apparatus for measuring by volume and delivering fluids or fluent solid materials, not provided for in the preceding groups for fluent solid material
- G01F13/005—Apparatus for measuring by volume and delivering fluids or fluent solid materials, not provided for in the preceding groups for fluent solid material comprising a screw conveyor
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01G—WEIGHING
- G01G13/00—Weighing apparatus with automatic feed or discharge for weighing-out batches of material
- G01G13/02—Means for automatically loading weigh pans or other receptacles, e.g. disposable containers, under control of the weighing mechanism
- G01G13/022—Material feeding devices
- G01G13/026—Material feeding devices by mechanical conveying means, e.g. belt or vibratory conveyor
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- General Physics & Mathematics (AREA)
- Fluid Mechanics (AREA)
- Flow Control (AREA)
- Weight Measurement For Supplying Or Discharging Of Specified Amounts Of Material (AREA)
Abstract
The present invention relates to a device for the control of dosing of a time dependent mass flow ~(t) for a helical dosing equipment (1) with a weighing machine (9) and a method of operation of such a device. The device includes modulation detector (31), with which the periodic deviation of the mass flow ~(t) from a target value can be analysed. The modulation detector (31) is connected to a speed modulator (32), with which the rotational speed f of the extraction helix (4) can be suitably phase shift modulated according to the curve shape derived by the modulation detector (31), whereby the deviations of the mass flow ~(t) are reduced to the unavoidable random deviations and the periodic deviation of the mass flow ~(t) can be eliminated. Both for the analysis of the mass flow ~(t) and also for the calculation of the modulation function analog or digital integrated electronic components can be applied.
Individual or all of these calculations can however also be performed with the aid of a digital computer.
Individual or all of these calculations can however also be performed with the aid of a digital computer.
Description
Dosing control for helical dosing equipment The present invention relates to a device for the control of dosing for a helical dosing equipment and to a s method for the operation of such devices.
In the conveying of bulk materials using an extraction helix the volumetric dosing principle or the more precise gravimetric principle can be used. In the latter the mass m(t) of an extraction equipment, a supply container and the bulk material present in it are weighed together, whereby the difference of mass per unit of time, namely the mass flow fi(t) dependent on the time t is continuously detected electronically. The actual value is compared to a desired target value and regulated by a known dosing controller to the desired value.
In practice the mass flow fi(t) dependent on the time t is however not constant, but fluctuates periodically at a frequency which equals the speed of revolution of the extraction helix or is a whole harmonic of it. The dosing controller is generally not in a position to even out these periodic deviations from the desired constant value.
In addition the difficulty exists that different extraction helices, and also different bulk materials, or the same bulk materials with slightly different or changing flow parameters lead to completely other fluctuations of the mass flow Ih (t).
In the conveying of bulk materials using an extraction helix the volumetric dosing principle or the more precise gravimetric principle can be used. In the latter the mass m(t) of an extraction equipment, a supply container and the bulk material present in it are weighed together, whereby the difference of mass per unit of time, namely the mass flow fi(t) dependent on the time t is continuously detected electronically. The actual value is compared to a desired target value and regulated by a known dosing controller to the desired value.
In practice the mass flow fi(t) dependent on the time t is however not constant, but fluctuates periodically at a frequency which equals the speed of revolution of the extraction helix or is a whole harmonic of it. The dosing controller is generally not in a position to even out these periodic deviations from the desired constant value.
In addition the difficulty exists that different extraction helices, and also different bulk materials, or the same bulk materials with slightly different or changing flow parameters lead to completely other fluctuations of the mass flow Ih (t).
The aim which is addressed by the present invention, is to produce a device for dosing control of helical dosing equipment as well as a method for the operation of such devices, which are immediately and always ready, and with which the above mentioned periodic fluctuations arising in the mass flow 1(t) of such devices can be essentially eliminated, independently of the characteristics of the extraction helix used and independent of the characteristics of different bulk materials.
According to a broad aspect of the present invention there is provided a device for dosing control of the mass flow for a helical dosing equipment with a supply container for bulk material, an electric motor, an extraction helix coupled to it, angle measuring means for determining the angular position of the extraction helix, a weighing machine which continuously measures the weight of the helical dosing equipment together with the bulk material contained in it, a mass flow controller connected to an output of the weighing machine and a rotational speed regulator connected to the motor, characterised in that a modulation detector is present and is connected to the angle measuring means, with which periodic deviations of a characteristic signal from a target value can be analysed quantitatively, a rotational speed modulator is present and is connected to the angle measuring means and the modulation detector, with which a suitable modulation signal can be generated from the quantitative values found by the modulation detector, a processing element is present and is connected to the rotational speed modulator and the mass flow controller, with which this modulation signal and the characteristic - 2a -signal for the mass flow can be processed into a modulated position signal, the rotational speed regulator is connected to an output of the processing element and with this modulated position signal can modulate the speed of revolution of the extraction helix according to the shape of the curve derived by the modulation detector.
According to a further broad aspect of the present io invention there is provided a method for the operation of a device for controlling the dosing of the mass flow for a helical dosing equipment with a supply container for bulk material, an electric motor, an extraction helix coupled to it, a weighing machine which continuously measures the weight of the helical dosing equipment together with the remaining bulk material contained in it with a mass flow controller connected to an output of the weighing machine and a rotational speed regulator connected to the motor, characterised in that the periodic deviations of the mass flow from a target value are continuously analysed by a modulation detector, an pproximation function is calculated for these deviations, the rotational speed of the extraction helix, corresponding to the calculated approximation function, is modulated using a rotational speed modulator such that the deviations of the mass flow are reduced to the unavoidable random deviations and the periodic deviations of the mass flow are eliminated.
According to a broad aspect of the present invention there is provided a device for dosing control of the mass flow for a helical dosing equipment with a supply container for bulk material, an electric motor, an extraction helix coupled to it, angle measuring means for determining the angular position of the extraction helix, a weighing machine which continuously measures the weight of the helical dosing equipment together with the bulk material contained in it, a mass flow controller connected to an output of the weighing machine and a rotational speed regulator connected to the motor, characterised in that a modulation detector is present and is connected to the angle measuring means, with which periodic deviations of a characteristic signal from a target value can be analysed quantitatively, a rotational speed modulator is present and is connected to the angle measuring means and the modulation detector, with which a suitable modulation signal can be generated from the quantitative values found by the modulation detector, a processing element is present and is connected to the rotational speed modulator and the mass flow controller, with which this modulation signal and the characteristic - 2a -signal for the mass flow can be processed into a modulated position signal, the rotational speed regulator is connected to an output of the processing element and with this modulated position signal can modulate the speed of revolution of the extraction helix according to the shape of the curve derived by the modulation detector.
According to a further broad aspect of the present io invention there is provided a method for the operation of a device for controlling the dosing of the mass flow for a helical dosing equipment with a supply container for bulk material, an electric motor, an extraction helix coupled to it, a weighing machine which continuously measures the weight of the helical dosing equipment together with the remaining bulk material contained in it with a mass flow controller connected to an output of the weighing machine and a rotational speed regulator connected to the motor, characterised in that the periodic deviations of the mass flow from a target value are continuously analysed by a modulation detector, an pproximation function is calculated for these deviations, the rotational speed of the extraction helix, corresponding to the calculated approximation function, is modulated using a rotational speed modulator such that the deviations of the mass flow are reduced to the unavoidable random deviations and the periodic deviations of the mass flow are eliminated.
The invention is further explained using the following Figures. Shown are:
Fig. 1 the basic schematic diagram of a helical dosing equipment according to the known state of the technology, Fig. 2 a representation of a position signal s(t) to the speed regulator and the resultant mass flow in(t) in a helical dosing equipment according to the known state of the technology, Fig. 3 the basic diagram of a device according to the invention for dosing control for a helical dosing equipment with a modulation detector and a rotational speed modulator, Fig. 4 the block circuit diagram of a modulation detector according to the invention, Fig. 5 the block circuit diagram of a rotational speed modulator according to the invention, Fig. 6 a representation of the modulated position signal smod(t) and the resultant mass flow m (t) .
Fig. 1 shows the basic design of a helical dosing equipment 1 according to the known state of the technology. It has a supply container 2 filled with bulk material, from which the bulk material falls via a guide 3 onto an extraction helix 4. This extraction helix 4 is as a rule connected via a gearbox 5 to an electric motor 6. Further, angle measuring means are present with which the angular position of the extraction helix 4 can be determined. Such means are known and include for instance coded discs or incremental transmitters which are connected to a suitable axle. Here, as an example, an incremental transmitter 8 is shown, which is connected to the axle of the electric motor 6. The whole helical dosing equipment 1 is positioned on an electronic weighing machine 9, which is of itself known. The sum of the masses of the helical dosing equipment 1 and of the bulk material contained in it is measured by the weighing machine 9. The corresponding weight signal is taken in a known manner to the input of an electronic differentiator 13 13. This has an output 10, which now gives out a signal, which corresponds to the mass flow m(t). This output 10 is connected to the first input 16 of a mass flow controller 18. A target value transmitter 20 generates at its output a first target value signal. Its output is connected to a second input 17 of the mass flow controller 18, which generates a position signal s(t) at its output, which is essentially corrected by the difference between the mass flow signal from the differentiator 13 and the signal from the target value transmitter 20. The output of the mass flow controller 18 is connected to a first input 24 of a rotational speed -regulator 25. The incremental transmitter 8 named above generates a speed signal, which is applied to the second input 26 of the speed regulator 25. This generates a difference signal at its output, which corresponds essentially to the difference between the position signal s (t) of the mass flow controller 18 and the speed signal of the incremental transmitter 8. The output of the speed regulator 25 is connected to the input of the electric motor 6, whereby the speed of rotation of the electric motor 6 is matched to the desired target value of the mass flow in(t).
Fig. 2 shows the progress over time of the essentially constant position signal s(t) at the first input 24 of the speed regulator 25, and the progress over time of the mass flow in (t) resulting from it in a helical dosing equipment 1 according to the known state of the technology. The speed of the extraction helix 4 selected as an example amounts here to a half turn per second, which gives a period duration T of two seconds. The position signal s(t) of the mass flow controller 18 has in this example a value of 40% of its maximum value. The resultant mass flow in(t) - similarly given as a fraction of its maximum value - shows a periodic progress with a period T, which is overlaid by random, a periodic interference. Experience shows the main part of the periodic interference to lie at the basic frequency f =
2n/T. The contributions of the harmonics 2f, 3f,... are practically negligible. The mass flow in(t) can, apart from random interference, be described mathematically as follows:
in(t) = A + Sl sin(l. 2nf.t) + Cl cos(1. 2nf.t) + S2 sin(2. 2nf.t) + C2 cos(2. 2rif.t) + S3 sin(3. 2nf.t) + C3 cos(3. 2nf.t) where A, S1, Cl, S2, C2, ... are constants, which fulfil the conditions A2 >> S12+C12 >>S22+C22>> ... The sampling frequency of the weighing machine 9 is here always much greater than the rotational speed of the extraction helix 4.
Fig. 3 shows the basic diagram of a device according to the invention for the control of dosing for a helix dosing equipment 1. It includes, as well as the means already described under Fig. 1, a modulation detector 31 in addition, with which the periodic deviations of a characteristic signal for the mass flow in(t)can be quantitatively analysed by a target value and a rotational speed modulator 32, with which a suitable modulation signal can be generated from the quantitative values found by the modulation detector 31, with which the position signal s(t) and thereby the speed of rotation of the extraction helix 4 is modulated corresponding to the curve shape of the mass flow in(t) derived by the modulation detector 31. The modulation of the position signal s(t) occurs in a first processing element 83, which has a first and a second input: one input 79 of the rotational speed modulator 32, which carries the modulation signal, is connected to the first input, the output of the mass flow controller 18, which carries the position signal s(t), is connected to the second input of the processing element 83. The two signals applied to its two inputs are processed in a suitable manner, for instance by mixing or by simple multiplication, into a single signal Smod(t). This signal Smod(t) is present on one output of the processing element 83, which is connected to the input 24 of the rotational speed regulator 25.
Below is presented in each case one technical embodiment of a modulation detector 31 and one of a rotational speed modulator 32.
The modulation detector 31 has a first input 33, which is connected to the output of the mass flow controller 18, whereby this input is indirectly connected to the weighing machine 9, and a second input 34, which as a rule via a divider element 44, is connected to the output of the angle measuring means, here, for instance, with the output of an incremental transmitter 8. In a modification the first input 33 can be connected directly to the output 10 of the weighing machine 9, instead of indirectly via the mass flow controller 18, as is indicated by the dashed connecting line. The necessary modifications to the details of the circuit are familiar to the specialist, for which reason it is unnecessary to go further into this here. At this first input 33 there is thus in both cases a signal which is characteristic of the mass flow in(t), which includes information on the deviation from its target value of the mass flow m(t), that is either the position signal s (t) of the mass flow controller 18 or the signal at the output 10 of the weighing machine 9, which below is always intended to be included under the concept of position signal s(t).
The modulation detector 31 has an output 39 and an output 40, which are connected respectively to corresponding inputs 62 and 63 of the rotational speed modulator 32. The rotational speed modulator 32 includes also a speed signal input 41. At this input 41 a signal is applied which is formed in a further processing element 85 from the signals of the divider element 44 and a known phase correction element 84, for instance by mixing. In a very simple modification this processing element 85 can be a simple addition element. The function of the phase correcting element 84 is treated further in the description of Fig. 5.
Fig. 4 shows the block circuit diagram of a modulation detector 31 according to the invention, with the use of an incremental transmitter 8 as the angle measuring means, which as a rule also makes necessary the application of a divider element 44. The characteristic signal for the mass flow in (t) , i.e. the position signal s(t) under which the signal at the output 10 of the weighing machine 9 is also understood, is applied to the first input 33 of the modulation detector 31. This position signal s(t) is first taken to an average value deviation element 42, which is known to the specialist and with which the deviation of the mass flow in (t) from its average value can be determined. The divider element 44 divides the signals from the incremental transmitter 8 applied to it by a suitable number, as a rule by the number of pulses from the incremental transmitter resulting per revolution of the extraction helix 4 and transmits this basic frequency f to a second input 34 of the modulation detector 31 as the rotational speed signal. The modulation detector 31 includes a first angle function generator 47, at whose input this rotational speed signal is applied. The angle function generator 47 has an S-output 48 and a C-output 49, at which essentially a sine and a cosine signal with the basic frequency f respectively are output. The modulation detector 31 further includes two multiplier elements 50, 51 which each have two factor inputs 52, 53, and 54, 55 respectively and each has a product output 56 and 57 respectively. The first factor input 53 of the first multiplier element 50 is connected to the S-output 48, its second factor input 52 to the output of the average value equalising element 42. The first factor input 55 of the second multiplier element 51 is connected in a corresponding manner to the C-output 49, its second factor input 54 similarly to the output of the average value equalising element 42. At the product output 56 of the first multiplier element 50 there appears essentially a product of the mass flow in(t) and a sine function with period T, at the product output 57 a product of the mass flow m(t) and a cosine function with the same period T.
Each of the product outputs 56, 57 is connected to one input of an integrator 60, 61 which integrate these signals over the time T and present the values of these integrals at their outputs 39, 40. At the output 39 there appears thereby essentially the value of S1 =T f in (t) .sin(2nf.t)dt and at output 40 correspondingly the value essentially of C1= 1 f in(t).cos(2nf.t)dt To i.e. the values of the two Fourier coefficients S1, Cl in the development of the periodic function in(t) as the sum of a constant function and the sine and cosine functions of suitable amplitude and basic frequency f.
Fig. 5 shows the block circuit diagram of a rotational speed modulator 32 according to the invention, similarly adapted to the example of the use of an incremental transmitter 8 as the means of angle measurement. At the rotational speed signal input 41 of the rotational speed modulator 32 appears the output signal of the processing element 85, already set out in the description of Fig. 3. This speed signal input 41 is connected to the input of a second angle function generator 67. This has an S-output 68 and a C-output 69, at which essentially a sine signal or a cosine signal, respectively with the basic frequency f are generated.
With the aid of the already mentioned phase correcting element 84 the phase setting of the angle function given out by the angle function generator 67 can be additionally shifted, which can be useful owing to the delayed system response times. The rotational speed modulator 32 has two further inputs 62 and 63, which are io joined to the outputs 39 and 40 respectively of the already presented modulation detector 31. It further includes two multiplying elements 70 and 71 which each has two factor inputs and one product output 74 and 75 respectively. Each of the inputs 62, 63 is connected with one of the two factor inputs of in each case one of these two multiplying elements 70 and 71 respectively, whilst the other factor inputs in each case are connected to the S-output 68 and the C-output 69 respectively of the second angle function generator 67. In the first multiplying element 70 the product is formed of the signal at the S-output 68 and the signal at the output 39, in the second multiplying element 71 is formed the product of the signal at the C-output 69 and the signal at the output 40 of the modulation detector 31. The rotational speed modulator 32 further includes an addition element 76, with which the signals at the product outputs 74, 75 can be added. These sums represent a matching phase shifted approximation function for the deviation from an average value of the mass flow in (t) . The output 79 of the addition element 76 is connected to one of the inputs of the processing element 83, as already set out in the description of Fig. 3. At the output of the processing element 83 thereby appears a signal from the mass flow controller 18 overlaid by a sine function of frequency f with matching amplitude and phase position, which can be taken to the first input 24 of the rotational speed regulator 25 as a modulated position signal Smod(t) Fig. 6 shows the progress over time of the modulated position signal smod(t) at the first input 24 of the rotational speed regulator 25 as well as the resulting mass flow in(t) in a helical dosing equipment 1 according to the invention. The speed of rotation of the extraction helix 4 here amounts to a half turn per second as in the example in Fig. 2. The position signal s(t) has here for instance during time t < 5T an essentially constant, typical value of 40% of its maximum value.
This results in the periodically fluctuating mass flow in(t) already described under Fig. 2 which is similarly given as a fraction of its maximum value. At time t = 5T
the phase shifted modulation of the position signal s(t) becomes effective at the first input 24 of the rotational speed regulator 25. The deviations of the mass flow in(t) are reduced for t > 5T to unavoidable random deviations, whilst the periodic part of the mass flow m(t) for t > 5T
can be practically entirely eliminated.
With sufficient resolution over time of the mass flow in(t) by the weighing machine 9 it is obviously possible in accordance with the invention that in an analog manner, additional coefficients of the Fourier series, for instance S2, C2; S3, C3;...are determined and the speed of revolution modulated accordingly. This is familiar to the specialist, so that a detailed description can be dispensed with here. The number of harmonics which can be evened out is limited by the sampling frequency of the weighing machine 9 and the known mathematical sampling theorem.
It is obviously also in accordance with the invention that individual or all the necessary mathematical operations can be performed by the application of one or more integrated analog circuit elements, by the application of one or more integrated digital circuit elements or by the application of a programmable digital computer.
In other embodiments of the device according to the invention, on the one hand special values only, for instance the extreme values, of the mass flow in(t) are determined by the modulation detector 31; on the other hand any desired further modulation functions can be laid down and instead of a sum of sine and cosine functions comprise a suitable overlay of quadratic functions, in the simplest case for instance by the opening of lower and higher parabolic sections, whereby the device and the method respectively are simplified, periodic deviations of the mass flow in(t) can nonetheless be satisfactorily eliminated.
It is similarly in accordance with the invention to combine this device with known means or with known methods, especially with calibration measurements performed at suitable time intervals over one or more periods T. This can for instance occur such that the procedure according to the invention for eliminating deviations with the basic frequency f is employed, i.e.
the periodic deviations of the mass flow m(t) from a target value at the basic frequency f are analysed continuously with a modulation detector 31 and an approximation function calculated for these deviations, whilst the amplitudes of the deviations at higher frequencies 2f, 3f ... are determined by the last calibration measurement in each case. The speed of the extraction helix 4 is then modulated according to a combination of the calculated approximation function for the basic frequency f and the amplitudes for the deviations at higher frequencies, similarly using a rotational speed modulator 32 so that the deviations of the mass flow in(t) are reduced to the unavoidable random and the periodic deviations of the mass flow in(t) are eliminated.
Fig. 1 the basic schematic diagram of a helical dosing equipment according to the known state of the technology, Fig. 2 a representation of a position signal s(t) to the speed regulator and the resultant mass flow in(t) in a helical dosing equipment according to the known state of the technology, Fig. 3 the basic diagram of a device according to the invention for dosing control for a helical dosing equipment with a modulation detector and a rotational speed modulator, Fig. 4 the block circuit diagram of a modulation detector according to the invention, Fig. 5 the block circuit diagram of a rotational speed modulator according to the invention, Fig. 6 a representation of the modulated position signal smod(t) and the resultant mass flow m (t) .
Fig. 1 shows the basic design of a helical dosing equipment 1 according to the known state of the technology. It has a supply container 2 filled with bulk material, from which the bulk material falls via a guide 3 onto an extraction helix 4. This extraction helix 4 is as a rule connected via a gearbox 5 to an electric motor 6. Further, angle measuring means are present with which the angular position of the extraction helix 4 can be determined. Such means are known and include for instance coded discs or incremental transmitters which are connected to a suitable axle. Here, as an example, an incremental transmitter 8 is shown, which is connected to the axle of the electric motor 6. The whole helical dosing equipment 1 is positioned on an electronic weighing machine 9, which is of itself known. The sum of the masses of the helical dosing equipment 1 and of the bulk material contained in it is measured by the weighing machine 9. The corresponding weight signal is taken in a known manner to the input of an electronic differentiator 13 13. This has an output 10, which now gives out a signal, which corresponds to the mass flow m(t). This output 10 is connected to the first input 16 of a mass flow controller 18. A target value transmitter 20 generates at its output a first target value signal. Its output is connected to a second input 17 of the mass flow controller 18, which generates a position signal s(t) at its output, which is essentially corrected by the difference between the mass flow signal from the differentiator 13 and the signal from the target value transmitter 20. The output of the mass flow controller 18 is connected to a first input 24 of a rotational speed -regulator 25. The incremental transmitter 8 named above generates a speed signal, which is applied to the second input 26 of the speed regulator 25. This generates a difference signal at its output, which corresponds essentially to the difference between the position signal s (t) of the mass flow controller 18 and the speed signal of the incremental transmitter 8. The output of the speed regulator 25 is connected to the input of the electric motor 6, whereby the speed of rotation of the electric motor 6 is matched to the desired target value of the mass flow in(t).
Fig. 2 shows the progress over time of the essentially constant position signal s(t) at the first input 24 of the speed regulator 25, and the progress over time of the mass flow in (t) resulting from it in a helical dosing equipment 1 according to the known state of the technology. The speed of the extraction helix 4 selected as an example amounts here to a half turn per second, which gives a period duration T of two seconds. The position signal s(t) of the mass flow controller 18 has in this example a value of 40% of its maximum value. The resultant mass flow in(t) - similarly given as a fraction of its maximum value - shows a periodic progress with a period T, which is overlaid by random, a periodic interference. Experience shows the main part of the periodic interference to lie at the basic frequency f =
2n/T. The contributions of the harmonics 2f, 3f,... are practically negligible. The mass flow in(t) can, apart from random interference, be described mathematically as follows:
in(t) = A + Sl sin(l. 2nf.t) + Cl cos(1. 2nf.t) + S2 sin(2. 2nf.t) + C2 cos(2. 2rif.t) + S3 sin(3. 2nf.t) + C3 cos(3. 2nf.t) where A, S1, Cl, S2, C2, ... are constants, which fulfil the conditions A2 >> S12+C12 >>S22+C22>> ... The sampling frequency of the weighing machine 9 is here always much greater than the rotational speed of the extraction helix 4.
Fig. 3 shows the basic diagram of a device according to the invention for the control of dosing for a helix dosing equipment 1. It includes, as well as the means already described under Fig. 1, a modulation detector 31 in addition, with which the periodic deviations of a characteristic signal for the mass flow in(t)can be quantitatively analysed by a target value and a rotational speed modulator 32, with which a suitable modulation signal can be generated from the quantitative values found by the modulation detector 31, with which the position signal s(t) and thereby the speed of rotation of the extraction helix 4 is modulated corresponding to the curve shape of the mass flow in(t) derived by the modulation detector 31. The modulation of the position signal s(t) occurs in a first processing element 83, which has a first and a second input: one input 79 of the rotational speed modulator 32, which carries the modulation signal, is connected to the first input, the output of the mass flow controller 18, which carries the position signal s(t), is connected to the second input of the processing element 83. The two signals applied to its two inputs are processed in a suitable manner, for instance by mixing or by simple multiplication, into a single signal Smod(t). This signal Smod(t) is present on one output of the processing element 83, which is connected to the input 24 of the rotational speed regulator 25.
Below is presented in each case one technical embodiment of a modulation detector 31 and one of a rotational speed modulator 32.
The modulation detector 31 has a first input 33, which is connected to the output of the mass flow controller 18, whereby this input is indirectly connected to the weighing machine 9, and a second input 34, which as a rule via a divider element 44, is connected to the output of the angle measuring means, here, for instance, with the output of an incremental transmitter 8. In a modification the first input 33 can be connected directly to the output 10 of the weighing machine 9, instead of indirectly via the mass flow controller 18, as is indicated by the dashed connecting line. The necessary modifications to the details of the circuit are familiar to the specialist, for which reason it is unnecessary to go further into this here. At this first input 33 there is thus in both cases a signal which is characteristic of the mass flow in(t), which includes information on the deviation from its target value of the mass flow m(t), that is either the position signal s (t) of the mass flow controller 18 or the signal at the output 10 of the weighing machine 9, which below is always intended to be included under the concept of position signal s(t).
The modulation detector 31 has an output 39 and an output 40, which are connected respectively to corresponding inputs 62 and 63 of the rotational speed modulator 32. The rotational speed modulator 32 includes also a speed signal input 41. At this input 41 a signal is applied which is formed in a further processing element 85 from the signals of the divider element 44 and a known phase correction element 84, for instance by mixing. In a very simple modification this processing element 85 can be a simple addition element. The function of the phase correcting element 84 is treated further in the description of Fig. 5.
Fig. 4 shows the block circuit diagram of a modulation detector 31 according to the invention, with the use of an incremental transmitter 8 as the angle measuring means, which as a rule also makes necessary the application of a divider element 44. The characteristic signal for the mass flow in (t) , i.e. the position signal s(t) under which the signal at the output 10 of the weighing machine 9 is also understood, is applied to the first input 33 of the modulation detector 31. This position signal s(t) is first taken to an average value deviation element 42, which is known to the specialist and with which the deviation of the mass flow in (t) from its average value can be determined. The divider element 44 divides the signals from the incremental transmitter 8 applied to it by a suitable number, as a rule by the number of pulses from the incremental transmitter resulting per revolution of the extraction helix 4 and transmits this basic frequency f to a second input 34 of the modulation detector 31 as the rotational speed signal. The modulation detector 31 includes a first angle function generator 47, at whose input this rotational speed signal is applied. The angle function generator 47 has an S-output 48 and a C-output 49, at which essentially a sine and a cosine signal with the basic frequency f respectively are output. The modulation detector 31 further includes two multiplier elements 50, 51 which each have two factor inputs 52, 53, and 54, 55 respectively and each has a product output 56 and 57 respectively. The first factor input 53 of the first multiplier element 50 is connected to the S-output 48, its second factor input 52 to the output of the average value equalising element 42. The first factor input 55 of the second multiplier element 51 is connected in a corresponding manner to the C-output 49, its second factor input 54 similarly to the output of the average value equalising element 42. At the product output 56 of the first multiplier element 50 there appears essentially a product of the mass flow in(t) and a sine function with period T, at the product output 57 a product of the mass flow m(t) and a cosine function with the same period T.
Each of the product outputs 56, 57 is connected to one input of an integrator 60, 61 which integrate these signals over the time T and present the values of these integrals at their outputs 39, 40. At the output 39 there appears thereby essentially the value of S1 =T f in (t) .sin(2nf.t)dt and at output 40 correspondingly the value essentially of C1= 1 f in(t).cos(2nf.t)dt To i.e. the values of the two Fourier coefficients S1, Cl in the development of the periodic function in(t) as the sum of a constant function and the sine and cosine functions of suitable amplitude and basic frequency f.
Fig. 5 shows the block circuit diagram of a rotational speed modulator 32 according to the invention, similarly adapted to the example of the use of an incremental transmitter 8 as the means of angle measurement. At the rotational speed signal input 41 of the rotational speed modulator 32 appears the output signal of the processing element 85, already set out in the description of Fig. 3. This speed signal input 41 is connected to the input of a second angle function generator 67. This has an S-output 68 and a C-output 69, at which essentially a sine signal or a cosine signal, respectively with the basic frequency f are generated.
With the aid of the already mentioned phase correcting element 84 the phase setting of the angle function given out by the angle function generator 67 can be additionally shifted, which can be useful owing to the delayed system response times. The rotational speed modulator 32 has two further inputs 62 and 63, which are io joined to the outputs 39 and 40 respectively of the already presented modulation detector 31. It further includes two multiplying elements 70 and 71 which each has two factor inputs and one product output 74 and 75 respectively. Each of the inputs 62, 63 is connected with one of the two factor inputs of in each case one of these two multiplying elements 70 and 71 respectively, whilst the other factor inputs in each case are connected to the S-output 68 and the C-output 69 respectively of the second angle function generator 67. In the first multiplying element 70 the product is formed of the signal at the S-output 68 and the signal at the output 39, in the second multiplying element 71 is formed the product of the signal at the C-output 69 and the signal at the output 40 of the modulation detector 31. The rotational speed modulator 32 further includes an addition element 76, with which the signals at the product outputs 74, 75 can be added. These sums represent a matching phase shifted approximation function for the deviation from an average value of the mass flow in (t) . The output 79 of the addition element 76 is connected to one of the inputs of the processing element 83, as already set out in the description of Fig. 3. At the output of the processing element 83 thereby appears a signal from the mass flow controller 18 overlaid by a sine function of frequency f with matching amplitude and phase position, which can be taken to the first input 24 of the rotational speed regulator 25 as a modulated position signal Smod(t) Fig. 6 shows the progress over time of the modulated position signal smod(t) at the first input 24 of the rotational speed regulator 25 as well as the resulting mass flow in(t) in a helical dosing equipment 1 according to the invention. The speed of rotation of the extraction helix 4 here amounts to a half turn per second as in the example in Fig. 2. The position signal s(t) has here for instance during time t < 5T an essentially constant, typical value of 40% of its maximum value.
This results in the periodically fluctuating mass flow in(t) already described under Fig. 2 which is similarly given as a fraction of its maximum value. At time t = 5T
the phase shifted modulation of the position signal s(t) becomes effective at the first input 24 of the rotational speed regulator 25. The deviations of the mass flow in(t) are reduced for t > 5T to unavoidable random deviations, whilst the periodic part of the mass flow m(t) for t > 5T
can be practically entirely eliminated.
With sufficient resolution over time of the mass flow in(t) by the weighing machine 9 it is obviously possible in accordance with the invention that in an analog manner, additional coefficients of the Fourier series, for instance S2, C2; S3, C3;...are determined and the speed of revolution modulated accordingly. This is familiar to the specialist, so that a detailed description can be dispensed with here. The number of harmonics which can be evened out is limited by the sampling frequency of the weighing machine 9 and the known mathematical sampling theorem.
It is obviously also in accordance with the invention that individual or all the necessary mathematical operations can be performed by the application of one or more integrated analog circuit elements, by the application of one or more integrated digital circuit elements or by the application of a programmable digital computer.
In other embodiments of the device according to the invention, on the one hand special values only, for instance the extreme values, of the mass flow in(t) are determined by the modulation detector 31; on the other hand any desired further modulation functions can be laid down and instead of a sum of sine and cosine functions comprise a suitable overlay of quadratic functions, in the simplest case for instance by the opening of lower and higher parabolic sections, whereby the device and the method respectively are simplified, periodic deviations of the mass flow in(t) can nonetheless be satisfactorily eliminated.
It is similarly in accordance with the invention to combine this device with known means or with known methods, especially with calibration measurements performed at suitable time intervals over one or more periods T. This can for instance occur such that the procedure according to the invention for eliminating deviations with the basic frequency f is employed, i.e.
the periodic deviations of the mass flow m(t) from a target value at the basic frequency f are analysed continuously with a modulation detector 31 and an approximation function calculated for these deviations, whilst the amplitudes of the deviations at higher frequencies 2f, 3f ... are determined by the last calibration measurement in each case. The speed of the extraction helix 4 is then modulated according to a combination of the calculated approximation function for the basic frequency f and the amplitudes for the deviations at higher frequencies, similarly using a rotational speed modulator 32 so that the deviations of the mass flow in(t) are reduced to the unavoidable random and the periodic deviations of the mass flow in(t) are eliminated.
Claims (19)
1. A device for dosing control of the mass flow ~(t) for a helical dosing equipment (1) with a supply container (2) for bulk material, an electric motor (6), an extraction helix (4) coupled to it, angle measuring means for determining the angular position of the extraction helix (4), a weighing machine (9) which continuously measures the weight of the helical dosing equipment (1) together with the bulk material contained in it, a mass flow controller (18) connected to an output (10) of the weighing machine (9) and a rotational speed regulator (25) connected to the motor (6), characterised in that - a modulation detector (31) is present and is connected to the angle measuring means, with which periodic deviations of a characteristic signal from a target value can be analysed quantitatively, - a rotational speed modulator (32) is present and is connected to the angle measuring means and the modulation detector (31), with which a suitable modulation signal can be generated from the quantitative values found by the modulation detector (31), - a processing element (83) is present and is connected to the rotational speed modulator (32) and the mass flow controller (18), with which this modulation signal and the characteristic signal for the mass flow ~(t) can be processed into a modulated position signal S mod(t) - the rotational speed regulator (25) is connected to an output of the processing element (83) and with this modulated position signal S mod (t) can modulate the speed of revolution of the extraction helix (4) according to the shape of the curve derived by the modulation detector (31).
2 A device according to Claim 1, characterised in that the angle measuring means include an incremental transmitter (8) joined to a suitable axle.
3. A device according to one of the claims 1 or 2, characterised in that - an output (10) of the weighing machine (9) is connected indirectly via the mass flow controller (18) to the modulation detector (31), - the characteristic signal for the mass flow ~ (t) is a position signal s(t) at the output of the mass flow controller (18).
4. A device according to one of the claims 1 or 2, characterised in that - an output (10) of the weighing machine (9) is connected directly to the modulation detector (31), - the characteristic signal for the mass flow ~(t) is a signal at the output (10) of the weighing machine (9).
5. A device according to one of the claims 2 to 4, characterised in that - a divider element (44) is present, - the incremental transmitter (8) is connected to this divider element (44), - this divider element (44) divides the frequency of a signal generated by the incremental transmitter (8) by the number of pulses from the incremental transmitter resulting per revolution of the extraction helix, - the incremental transmitter (8) is connected indirectly via the divider element (44) to the modulation detector (31).
6. A device according to one of the claims 2 to 4, characterised in that - a divider element (44) is present, - the incremental transmitter (8) is connected to this divider element (44), - this divider element (44) divides the frequency of a signal generated by the incremental transmitter (8) by the number of pulses from the incremental transmitter resulting per revolution of the extraction helix, - the incremental transmitter (8) is connected indirectly via the divider element (44) to the rotational speed modulator (32).
7. A device according to one of the claims 1 to 6, characterised in that - the modulation detector (31) includes, suitably connected amongst each other - means (42) with which the periodic deviations from the average value of the mass flow ~(t) - from a target value can be determined - means (47) for generating a sine and a cosine signal at the basic frequency f, - multiplication means (50, 51) with which the products of the mass flow ~(t) and the sine signal, and of the mass flow ~(t) and the cosine signal can be determined, - means of integration (60, 61), with which the average values in each case of these products can be determined over time.
8. A device according to claim 7, characterised in that in the modulation detector (31) - additional means are available for the generation of sine and cosine signals at a natural multiple of the basic frequency f, - additional means are available for the determination of the average values over time of the products of the mass flow in(t) and the these sine and cosine signals respectively.
9. A device according to one of the claims 1 to 6, characterised in that - the rotational speed modulator (32) includes, - suitably interconnected amongst each other means (67) for the generation of one sine and one cosine signal respectively at frequency f - multiplication means (70, 71) with which these sine and cosine signals respectively can be multiplied with the corresponding output signals from the modulation detector (31), addition means (76), with which these products can be added into a sum, - the rotational speed modulator (32) has an output (79), at which essentially a modulation signal appears which corresponds to this above mentioned sum, - this output (79) is connected with an input of the processing element (83).
10. A device according to claim 9, characterised in that in the rotational speed modulator (32) - additional means are available for the generation of sine and cosine signals at a natural multiple of the basic frequency f, - additional means are available to determine average values over time of the products of the mass flow ~(t) and these sine and cosine signals respectively.
11. A device according to claim 9, characterised in that - a divider element (44) is available, - the incremental transmitter (8) is connected to this divider element (44), - this divider element (44) divides the frequency of a signal generated by the incremental transmitter (8) by the number of pulses from the incremental transmitter resulting per revolution of the extraction helix, - a phase corrector element (84) is present, - a processing element (85) with two inputs is available, - the divider element (44) and the phase corrector element (84) are connected each to one input of this processing element (85), - the output of the processing element (85) is connected to the rotational speed signal input (41) of the rotational speed modulator (32), whereby the phase conditions of the angular functions generated by the angle function generator (67) of the rotational speed modulator (32) can be shifted.
12. A device according to one of the claims 1 to 11, characterised in that an integrated analog circuit element is applied in the device for the performance of at least one of the mathematical operations.
13. A device according to one of the claims 1 to 11, characterised in that an integrated digital circuit element is applied in the device for the performance of at least one mathematical operation.
14. A device according to one of the claims 1 to 11, characterised in that - a digital computer is present and suitably connected with the device, - this digital computer is applied in the device for the performance of at least one of the mathematical operations.
15. A method for the operation of a device for controlling the dosing of the mass flow it(t) for a helical dosing equipment (1) with a supply container (2) for bulk material, an electric motor (6), an extraction helix (4) coupled to it, a weighing machine (9) which continuously measures the weight of the helical dosing equipment (1) together with the remaining bulk material contained in it with a mass flow controller (18) connected to an output (10) of the weighing machine (9) and a rotational speed regulator (25) connected to the motor (6), characterised in that - the periodic deviations of the mass flow ~(t) from a target value are continuously analysed by a modulation detector (31), - an approximation function is calculated for these deviations, - the rotational speed of the extraction helix (4), corresponding to the calculated approximation function, is modulated using a rotational speed modulator (32) such that the deviations of the mass flow ~(t) are reduced to the unavoidable random deviations and the periodic deviations of the mass flow ~(t) are eliminated.
16. A method according to Claim 15, characterised in that - the mass flow ~(t) is continuously determined using a sampling frequency, which is large compared to the basic frequency f, - the coefficients of at least the basic frequency f in the Fourier series of the mass flow ~(t) are determined, - these coefficients are intermittently calculated and from them an approximation function for the time dependent deviation of the mass flow ~ (t) from an average value is calculated, - the speed of rotation of the extraction helix (4) is modulated in accordance with this approximation function.
17. A method in accordance with one of claims 15 or 16, characterised in that for the determination of the approximation function for the time dependent deviation of the mass flow ~ (t) from its target value the extreme values of the deviation of the mass flow ~ (t) are used.
18. A method in accordance with one of claims 15 to 17, characterised in that for the approximation function an overlay of a most quadratic function is used.
19. A method in accordance with Claim 15, characterised in that - the periodic deviations of the mass flow ~ (t) from a target value with the basic frequency f are continuously analysed using a modulation detector (31), - an approximation function is calculated for these deviations, - at suitable intervals of time a calibration measurement is performed over at least a period of T, - amplitudes of the periodic deviations of the mass flow ~ (t) from its target value with a higher frequency than the basic frequency f are determined from these calibration measurements, - the speed of rotation of the extraction helix (4) corresponding to a combination of the calculated approximation function for the basic frequency f and the amplitudes of the deviations of higher frequency is modulated by a rotational speed modulator (32), so that the variations of the mass flow ~ (t) are reduced to unavoidable random variations and the periodic deviations of the mass flow ~ (t) are eliminated.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CH633/00 | 2000-04-01 | ||
| CH6332000 | 2000-04-01 | ||
| PCT/CH2000/000656 WO2001048444A1 (en) | 2000-04-01 | 2000-12-11 | Dosing device for a worm dosing device |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2365119A1 CA2365119A1 (en) | 2001-07-05 |
| CA2365119C true CA2365119C (en) | 2011-07-19 |
Family
ID=4524901
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA2365119A Expired - Lifetime CA2365119C (en) | 2000-04-01 | 2000-12-11 | Dosing control for helical dosing equipment |
Country Status (4)
| Country | Link |
|---|---|
| US (1) | US6702152B1 (en) |
| EP (1) | EP1181507B1 (en) |
| CA (1) | CA2365119C (en) |
| WO (1) | WO2001048444A1 (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7270249B1 (en) * | 2005-03-03 | 2007-09-18 | Burkhead Ronnie J | Pneumatic metering apparatus for flowable solids product |
| DE102006061818B4 (en) * | 2006-12-21 | 2013-07-25 | Erwin Bichler | Discharge device for powdered or granular solids of fertilizer or animal feed dosing-mixing plants and method for operating such a device |
| CN102470365B (en) * | 2009-07-24 | 2014-12-17 | Emd密理博公司 | Feed bag construction |
| DE102010009753B4 (en) * | 2010-03-01 | 2014-09-18 | Schenck Process Gmbh | Device and method for dosing control of bulk material |
| DE102022102514A1 (en) | 2022-02-03 | 2023-08-03 | Schenck Process Europe Gmbh | Method or system for determining weighing signal correction values, for determining a corrected mass flow and for controlling a mass flow |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL7410941A (en) | 1974-06-04 | 1975-12-08 | Schenck Ag Carl | METHOD AND DEVICE FOR REGULATING THE DRAIN FROM A SILO. |
| US4320855A (en) * | 1976-12-07 | 1982-03-23 | Acrison, Incorporated | Weigh feeding apparatus |
| DE2903259C2 (en) | 1979-01-29 | 1986-04-10 | Carl Schenck Ag, 6100 Darmstadt | Process for dosing materials with changing flow properties |
| US4272824A (en) * | 1979-08-17 | 1981-06-09 | Pennant Products, Inc. | Batch product preparation |
| JPS5728217A (en) | 1980-07-29 | 1982-02-15 | Asano Seiki Kk | Measuring device for amount of supply of powder material |
| US5184754A (en) | 1990-10-18 | 1993-02-09 | Hansen Thomas N | Weight-controlled particulate matter feed system |
| US5423456A (en) | 1994-01-03 | 1995-06-13 | Larry V. Arendonk | Apparatus for continuous flow weighing |
| US6168305B1 (en) * | 1998-02-27 | 2001-01-02 | Merrick Industries, Inc. | System for precisely controlling discharge rates for loss-in-weight feeder systems |
| US6060667A (en) * | 1998-03-24 | 2000-05-09 | Pollock; John | Method and apparatus for supplying predefined quantities of bulk material |
-
2000
- 2000-11-12 US US10/018,471 patent/US6702152B1/en not_active Expired - Lifetime
- 2000-12-11 EP EP00979312.6A patent/EP1181507B1/en not_active Expired - Lifetime
- 2000-12-11 WO PCT/CH2000/000656 patent/WO2001048444A1/en active Application Filing
- 2000-12-11 CA CA2365119A patent/CA2365119C/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| CA2365119A1 (en) | 2001-07-05 |
| EP1181507B1 (en) | 2016-10-19 |
| EP1181507A1 (en) | 2002-02-27 |
| WO2001048444A1 (en) | 2001-07-05 |
| US6702152B1 (en) | 2004-03-09 |
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